In a pit at the Dmanisi excavation, Marc Meyer, at right, and Dato Taktakishvili set aside their digging tools to examine the skull of a hominin, or human ancestor, buried among a jumble of animal bones. The skull, one of four found at the site, belonged to a member of Homo erectus, a species with a brain about half the size of a modern human's. Archaeologists here have also excavated more than 5,000 animal bones, ranging from saber-toothed cats to extinct ancestors of elephants and giraffes.